Citi is still in need of reinvention. Even after rising more than 6% Wednesday, the stock trades at 70% of tangible book value. In other words, investors continue to believe Citi is worth more broken up than alive.

Such discounts to net worth, which are seen at many other global banks, reflect deep-seated questions about banking business models in light of changing financial markets, tougher regulation and the superlow interest-rate environment. This is prompting firms to rethink their structures.

The most dramatic example has been the announcement by Swiss giant UBS that it would essentially exit from the fixed-income trading business. Citi's most recent move isn't along those lines in terms of scale and scope, although it is an important step.

Not that Corbat, who only came into the CEO's job after the surprise ouster of former chief Vikram Pandit in October, could have been expected to undertake a major restructuring so early. His first task was presenting a budget for 2013 to Citi's board by early December.

In that sense, Wednesday's "repositioning" could be seen as tactical. The bank said it would close or sell some consumer-banking operations in markets outside the US, while also cutting some branches at home. It will look to trim back-office operational and technology expense. And it will streamline some of its capital-markets business, particularly in the cash equities business.

This will result in a roughly $1bn charge in the fourth quarter, although Citi expects to realise annual cost savings of about $900mn in 2013 and $1.1bn the year after. The expense base for Citi's main businesses was $44.5bn in 2011.

What investors ultimately want to hear, though, is whether Corbat will set a new strategic direction for the bank, replete with exits from some businesses.

"The real test will be what else Citigroup does prior to the annual meeting" next April, CLSA analyst Mike Mayo said. "As UBS has shown, exiting an entire business has a positive multiplier effect on your expense base, and it's the exiting that would be a ground-moving event for Citi."

One important area to watch is how Corbat deals with the bank's so-called Citi Holdings unit, which houses $171bn of businesses and assets the bank plans to dispose of. These are a drag on Citi's overall returns.

While investors would love that weight to be lifted, Citi finance chief John Gerspach, speaking Wednesday at the Goldman Sachs Financial Services conference, underscored the challenges in winding down these assets at a faster pace.

Another issue: Corbat has to weigh any even bigger moves during his honeymoon period against the desire of many shareholders for returns of capital. The bank, along with others, has to submit a capital plan to regulators in early January and undergo its annual "stress test."

The wiser long-term option may be for Corbat to chart a clear new course before trying to return capital, even if this causes some investor unrest.

Corbat is off to a strong start. But for his next move to count, it will likely need to be far more controversial.